Introduction

New York Times bestseller and author of the 4-Hour Body, Tim Ferris, recommends using cinnamon to reduce the glycemic load of food. That’s just the latest in a long list of supposed benefits of this exotic spice. Among its many claims to fame (apart from being a fabulous culinary spice) are being an anti-inflammatory, cold remedy, tooth powder, mouth freshener, carminative, antiseptic and astringent.

Many years ago, cinnamon was a valuable commodity that was moved along the spice trade route. With the advantage of modern science, we can now ask if there was any benefit (apart form economics ) to bringing cinnamon along the spice trade route centuries ago?

What Is Cinnamon?

Cinnamon (肉桂 ròu guì) is derived from a Greek word and means sweet wood. It belongs to the Lauraceace family.

Over 250 species of cinnamon have been identified to date. There are two main varieties of cinnamon:

  • the Ceylon or true cinnamon (Cinnamon zeylanicum Blume) native to Sri Lanka and Southern India
  • and cassia (Cinnamon aromaticum Ness) native to China, Indonesia and Vietnam.

The yield from the bark varies from region to region and depends on the age of the bark and the section of the bark used (top, center and lower sections). Cinnamon has been used in food preparations and in traditional medicine by the Egyptians and the Chinese since ancient antiquity.

A forensic examination of the body of John Plantagenet of Lancaster, first Duke of Bedford (died 1435 AD) showed that cinnamon was probably one the the agents used in the embalming process. (I like the smell of cinnamon very much but would not like to be embalmed in it and have to smell it forever).

Cinnamon contains over 41 volatile compounds. The most important constituents of cinnamon are:

  • cinnamaldehyde
  • trans-cinnanioldehyde
  • procyanidins
  • polyphenols (rutin, catechin, quescetin and kaempferol).

Cinnamaldehyde has anti-tyrosinase activity that suppresses hyper pigmentation and browning of fruit and vegetables (not humans unfortunately). This is also the fraction of cinnamon that is responsible for the spicy taste of cinnamon.

The yield of cinnamaldehyde varies between the different types of cinnamon trees. The essential oils from Cinnamon cassia contain 80–90% cinnamaldehyde with little or no eugenol, while C. zeylanicum bark contains 60–80% cinnamaldehyde and approximately 2% eugenol.

There are over 150,000 cinnamon related products for sale on Amazon including power, sticks, incense, capsules and oil. Cinnamon costs approximately $1 per ounce.

Is There Any Research?

There are 2014 publications related to cinnamon which includes 62 clinical trials. To put this into context, there are 3000 publications on ginger including 300 clinical trials.

Does It Benefit Skin Health?

DoTerra are a leading supplier of essential oils worldwide. Researchers from DoTerra published a paper in 2017 that opens with the line ‘The effect of cinnamon (Cinnamomum zeylanicum) bark essential oil (CBEO) on human skin cells has not been elucidated’ (21).

If DoTerra admit that there are no studies on the dermatological health of skin, then we can pretty much guess that this is the case (or at worst there are no positive studies)

They investigated the activity of a commercially available (aka their own brand) of cinnamon in a validated human dermal fibroblast system, a model of chronic inflammation and fibrosis and found it to be ‘is a promising anti-inflammatory agent; however, further research is required to clarify its clinical efficacy’ .

Bottom Line

Even the leading manufacturer of cinnamon oil admit that there is no proof that cinnamon helps skin health.

Is Cinnamon High in Antioxidants? Does It Have Anti Inflammatory Properties?

Brazilian investigators set about examining the effect of cinnamon in laying quails on the expression of genes related to antioxidant activity and lipid metabolism (1). A total of 144 Japanese quail (Coturnix japonica) were randomized to either no cinnamon supplementation or cinnamon supplementation (9g/kg of cinnamon powder).

Following a bewildering analysis of fatty acid synthase, acetyl-CoA carboxylase, apolipoprotein, estrogen receptor, superoxide dismutase and glutathione peroxidase, the authors conclude that cinnamon exerted an antioxidant effect and enhanced laying performance of the quails.

French investigators studied cinnamon extract on the antioxidant status of 22 subjects with impaired glucose and/or high body mass index (2).Subjects were randomised to placebo or cinnamon for 12 weeks. The study found that cinnamon had positive effects on the antioxidant status of the study subjects. The full paper was not available on PubMed which made it difficult to asses the fine print and statistics of this study

A single clinical trial looked at the role of 10 dietary supplements each day (100 mg of resveratrol, a complex of 800 mg each of green, black, and white tea extract, 250 mg of pomegranate extract, 650 mg of quercetinquercetin, 500 mg of acetyl-l-carnitine, 600 mg of lipoic acid, 900 mg of curcumin, 1 g of sesamin, 1.7 g of cinnamon bark extract, and 1.0 g fish oil) versus placebo in 56 adults over 6 months (3).

The study showed that this complex dietary supplement did not alter body fat measured by DEXA, blood pressure, plasma lipids, glucose, insulin, IGF-1, and markers of inflammation or oxidative stress. The authors of the paper concluded that  cinnamon exerted no positive cardiovascular or metabolic effects in non-obese relatively healthy individuals.

A third study from researchers in Iran aimed to determine the effect of herbal treatment on BP, endothelial function and anthropometric measures in patients with type 2 diabetes mellitus (4). A total of 204 patients were randomized to one of 5 intervention groups over 8 weeks:

  • cinnamon 3 gm + 3 glasses of black tea
  • cardamon 3 gm + 3 glasses of black tea
  • saffron 1 gm + 3 glasses of black tea
  • ginger 3 gm  + 3 glasses of black tea or
  • 3 glasses of black tea.

The herbal product failed to produce any significant effects on oxidation or inflammation. Positive effects were noted on plasma glucose and lipids and these results will be discussed later in this article.

Bottom Line

There is no robust evidence to support cinnamon as an antioxidant or anti-inflammatory.

Does It Protect Heart Health?

The Iranian study mentioned in the above section noted statistically significant effects of the herbal mixture on total cholesterol, HDL and LDL levels (4).

Another paper by the same group studied the same herbal mixture for BP control in patients with type 2 diabetes (5).

A total of 204 patients were randomized to one of 5 intervention groups over 8 weeks:

  • cinnamon 3 gm + 3 glasses of black tea
  • cardamon 3 gm + 3 glasses of black tea
  • saffron 1 gm + 3 glasses of black tea
  • ginger 3 gm  + 3 glasses of black tea or
  • + 3 glasses of black tea.

No significant difference was noted among the treatment groups in terms of BP control.

Finally a Canadian group conducted a review of the effect of short-term administration of cinnamon on blood pressure regulation in patients with pre diabetes (6).

They concluded that ‘Consumption of cinnamon (short term) is associated with a notable reduction in systolic BP and diastolic BP. Although cinnamon shows hopeful effects on BP-lowering, it would be premature to recommend cinnamon for BP control because of the limited number of studies available’.

Bottom Line

There is insufficient evidence to recommend cinnamon for heart health.

Does it Fight Diabetes?

The WHO predicts that by 2030 that diabetes mellitus will be the seventh leading cause of death worldwide. Cinnamon bark has been shown to improve sugar levels in a number of studies. A substance from cinnamon has been identified and coined ‘insulting potentiating factor’.

There are two main forms of diabetes.

  • Type 1 is an autoimmune disorder that typically occurs in children and young adults. In type 1 diabetes, the pancreas does not produce any insulin.
  • Type 2 diabetes tends to occur in older patients. In type 2 diabetes, the pancreas produces insulin but the cells are resistant to the insulin.

Cinnamon may help people with type 2 diabetes but has no role in type 1 diabetes.

People with type 1 diabetes need to take insulin on a daily basis and the discussion that follows is restricted to people with type 2 diabetes only.

The link between diabetes control and cinnamon was first published in the scientific literature in 2003 (7).

The study carried out by investigators in Pakistan looked at 60 patients with type 2 diabetes. The study showed that twice daily doses of cinnamon (1, 3 or 6 gms) lowered fasting glucose  levels by 18-29% and total cholesterol by 7-29%.

A Cochrane in 2012 review identified 10 randomised controlled trials of cinnamon involving 577 diabetic participants (8). Cinnamon was administered at in tablet or capsule form at a mean dose of 2gm/daily for 4 -16 weeks. Overall the studies were deemed to be of poor quality. The cinnamon was well tolerated.

However the cinnamon was no more effective than placebo or no treatment in reducing blood sugar or HbA1C (which is a long term measure of glucose control).

This 2012 Cochrane review was updated in 2013 by a collaboration of pharmacists and doctors from the USA in a meta-analysis that included 10 randomized control trials including 543 patients.  (9).

This meta-analysis found that cinnamon consumption is associated with a significant decrease in fasting blood sugar, total cholesterol and triglyceride levels and an increase in HDL levels but had no effect on HbA1C levels.

It is hard to explain how cinnamon would effect fasting blood sugar but not HbA1C. HbA1C reflects sugar levels over the preceding 12 weeks. One possible explanation could be that the studies were short-term i.e  less than 12 weeks which means that changes were seen in the blood glucose but not the HbA1C. Either way it is unsatisfactory.

Bottom Line

There may well be a link between cinnamon and diabetes. However the data is unclear at this time.

Does It Help The Brain? Protect Against Cognitive Decline?

There is interest in the possible protective role of cinnamon against cognitive decline. A group of researchers from Iran published a review paper in this in Pharmacy Res just last month (10).

The review noted that extract of cinnamon can inhibit tau accumulations, amyloid aggregation and toxicity in in vivo and in vitro models. Cinnamon modulates endothelial functions and attenuates vascular cell adhesion molecules.

At the end of the day, the authors conclude that further molecular and translational research studies as well as prolonged clinical trials are required to establish the therapeutic safety and efficacy of cinnamon for brain health.

Bottom Line

Cinnamon is promising but unproven for brain health.

Does It Lower Cancer Risk?

There is significant interest in spices in general for the prevention and treatment of cancer (11) There are no human clinical trials looking at cinnamon  for cancer.

There is a single in vitro study which shows that cinnamon has anti-cancer properties in liver cancer (12). A number of review papers on cinnamon boldly state that cinnamon has potential as an anti-colon cancer agent. There is a single paper that looked at the in vitro effect of cinnamon-oregano lipid nanoparticles as carriers for 5 fluoruracil for colon cancer (13).

The cinnamon-oregano vehicle improved the delivery of fluorouracil which allowed for the administration of lower doses of fluorouracil (and less toxicity). However it is important to note that the cinnamon was just an efficient vehicle for transporting fluorouracil and was not the active chemotherapeutic agent.

Another study found that cinnamon (trans-cinnamic aldehyde) was a potent potent activator of an antioxidant (Nrf2) response in cultured human epithelial colon cells (14). The investigators concluded cinnamon extract that may be a chemopreventive dietary factor targeting colorectal carcinogenesis.

A combination of cinnamon and cardamom in mice with colon cancer has been shown to enhance the level of detoxifying enzyme (GST activity)along with a decrease in lipid peroxidation levels (15)

This is all very interesting but not clinically relevant at this time.

Bottom Line

There is no evidence to support cinnamon in cancer.

Does It Fight Infections, Candida and Viruses?

In clinical practice we are seeing a growing number of infectious pathogens which are becoming resistant to the anti-microbial agents that we have. There are concerns that the rate of development of resistance in pathogens may outstrip the rate of development of new drugs – the predicted doomsday ‘post-antibiotic era’ scenario.

Plants have natural anti-infectious properties that they use to ward off predators. Essential oils are key among the plant defences. There is growing interest in the role of essential oils as infectious disease agents.

That being said, there us only a single clinical study looking at the antimicrobial properties of cinnamon.

A pilot study of five patients with HIV infection and fluconazole resistant oral candidiasis showed clinical improvement with a commercially available cinnamon preparation for one week (16) Otherwise there is only in vitro data showing that cinnamon shows some activity against Hepatitis C, H1N1, staph aureus, MRSA, strep pneumonia, resistant pseudomonas and nematodal infections.

Broth dilution studies shoed that cinnammon had an effect against the gram negative bacteria, pseudomonas (17). There is an interesting paper which suggests that preliminary in vitro work shows that cinnamon prevents biofilm formation by staph epidermis on metal work (18)

You may well ask why biofilms are oh so interesting. Literally everyday I see new patients who have infected orthopaedic implants. These infections can be really troublesome and may necessitate a long course of intravenous antibiotics or removal of the metalwork (which can be very difficult if the fracture has not yet healed).

Staph epidermidis creates a biofilm which makes it exceptionally difficult for antibiotics to reach it. I am always interested in anything that may just help these patients but realistically it will be quite some time before the required research is done for us to know if we can turn this ‘pilot study theory’ into everyday clinical practice.

Bottom Line

It is too early to comment on the infectious diseases properties of cinnamon. Technically, I should say that cinnamon is unproven an an anti-microbial but I am choosing to say that it is too early as we really need alternative infectious diseases agents.

Does It Assist With Dental Health?

A meta-analysis of all essential oils was published in 2015 in the Journal of International Society of Preventive and Community Dentistry. The reviewers concluded that ‘essential oils have the potential to be developed as a preventive or therapeutic agent for oral diseases but that further trials are needed to establish their safety and efficacy’ (19)

There is only one human clinical trial looking specifically at cinnamon in dental health (20)

In this study, a total of 115 healthy dental and medical students (aged 21 to 25 years) were randomly divided into three groups: i.e., the cinnamon group, the chlorhexidine gluconate mouthwash group and the placebo (distilled water) group. The chlorhexidine group showed the maximum decrease in both plaque and gingival scores, followed by cinnamon extract. However  the results did not reach the level of  statistical significance.

Bottom Line

Cinnamon has not been shown to promote dental health. In a later section, we will see some side effects of cinnamon related to dental and oral health.

Does It Help Fight Allergies?

There is a very definite relationship between cinnamon and allergy. Only slight problem is that the vast majority of the human publications implicate cinnamon as causing and not curing allergies.

We will look at both.

One study showed that cinnamon inhibited mast cell degranulation (which is a step in the allergy cascade) in vitro and in a mouse model which would be a good thing (22).

There are numerous case studies of oral contact dermatitis related to cinnamon dental products which one researcher published under the title ‘Cinnamon, spice and everything not nice’ (23).

There are also cases of oral allergic dermatitis related to cinnamon chewing gum (24). It has even been associated with allergy in deodorizing shoe insoles and coffee flavoring (25). Cinnamon has been associated with occupational allergy in an Italian baker and workers exposed to cinnamon tree bark (26).

Bottom Line

The association between allergy and cinnamon is the wrong kind of association as cinnamon has been listed as the cause of a wide range of allergic reactions.

Is Cinnamon (And The Extract) Safe?

In addition to the long list of cinnamon allergies, there are other specific side effects reported with cinnamon.

The cinnamon challenge is a popular internet dare that involves consuming one tablespoon of cinnamon in one minute without taking any liquids. Definitely, do not try this at home. The powder quickly dries the mouth making it difficult to swallow the remaining powder. This frequently causes coughing and sometimes aspiration of cinnamon into the lungs. The cellulose fibres of cinnamon are caustic and neither dissolve nor biodegrade in the lungs which poses a risk for ongoing lung fibrosis and lung damage (27)

Cinnamon is also used as a drug of misuse. A total of 32 cases of cinnamon oil abuse by male teenagers was reported to the Pittsburgh Poison Center over a five month period (28).

Conclusion

Sri Lankan investigators did a meta-analysis of all papers (70 in total after removal of duplicates) relating to the medicinal value of true’ cinnamon up until 2012 (29). They concluded that :

The available in-vitro and in-vivo evidence suggests that cinnamon has many beneficial health effects. However, since data on humans are sparse, randomized controlled trials in humans will be necessary to determine whether these effects have public health implications’.

Mr Tim Ferris, I really liked the 4-Hour Work Week (more than the 4-Hour Body) but the science simply does not support your claims about cinnamon.

I will continue to add cinnamon to my soy latte because I like it and not because I am deluded that it will actually help me.